Determination of Σ−Λ Relative Parity

An experiment has been performed to determine the $\ensuremath{\Sigma}\ensuremath{-}\ensuremath{\Lambda}$ relative parity, through a study of the decay mode ${\ensuremath{\Sigma}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}+{e}^{+}+{e}^{\ensuremath{-}}$. The ${\ensuremath{\Sigma}}^{0}$ were produced by stopping ${K}^{\ensuremath{-}}$ mesons in the Brookhaven National Laboratory-Columbia 30-in. hydrogen chamber, in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{0}+{\ensuremath{\pi}}^{0}$, and 314 events were identified. The experimental distribution of the combined mass of the electron-positron pair was compared to that predicted by Feinberg, by Feldman and Fulton, and by Evans. If it is assumed that the dependence of the form factors on the combined mass of the electron-positron pair can be neglected, and that the ratio of the electric form factor ${F}_{1}$ to the magnetic form factor ${F}_{2}$ is less than 6, then the data show that the $\ensuremath{\Sigma}\ensuremath{-}\ensuremath{\Lambda}$ relative parity is even.